You should be able to remove the Wordpad association by simply selecting the appropriate (rsr) file type in the file types tab and clicking 'Remove.' After that, the files will show up in Explorer as simply "rsr file." This worked for me in testing. Poser is kind of schizophreniz, using the rsr extention for two different file types, rsr are used for thumbnail images in Poser 4 and also for compressed geometry files (the rsr files in the geometries folder).

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